Background of the Invention
This invention relates to material conveyor systems and more particularly to material conveyor systems that utilize free-roaming apparatus such as robots for application in a work area, such as a factory and still more particular to material conveyor systems that utilize television cameras as a means of tracking and guiding the free roaming mobile apparatus.
Vehicular navigation is used particularly for the guidance of airplanes, ships and spacecrafts. Its simplest forms, dead reckoning, is relatively inaccurate and useful only for extrapolation from known fixed points. Celestial navigation is possible only outdoors or in space. Other well developed techniques are loran, radar, directional radio, satellite doppler, and internal inertia guidance systems. Most of the above numerated methods and apparatus are inappropriate in a closed environment setting such as manufacturing facilities, while still others which may be applicable are prohibitively costly.
It is desirable to use free-roaming robots as material handlers or conveyors in a factory operation such as the semiconductor manufacturing operation because of their inherent cleanliness and extreme flexibility. The transportation of unfinished material is a problem common to all factories. The problem is typically solved through the use of fork lift trucks, rail cars, pneumatic tubes, conveyor belts, or simply by carrying the material by hand. The automatic techniques such as rails, belts, and tubes suffer from inflexibility. That is, the automatic techniques can only pick up and deposit materials at predetermined positions in a fixed pattern which is not easily changed.
Automatic vehicles which are guided by a buried electrical wire are commonly used, and are a refinement of rail car techniques. A wire is buried beneath the floor along the desired path. The car tracks the wire and stops at predetermined positions or stations. The wire may be a single loop, or can have branch points at which cars must select one of several possible paths. Cars must stay on the wire and cannot stray. Before the car can visit a new station, a new wire must be buried and electrified. Temporary route or scheduled changes are impractical when the paths are fixed or fused.
For a robotic guided vehicle to be free of the restrictions of fixed guide paths, it is necessary to provide a position sensory system. The position of the robot while moving must be known precisely enough to navigate narrow doorways and to avoid collisions. The stationary position of the robot must be known precisely enough to allow it to perform all tasks at the station and to load and unload materials for transport.